Rtc Clocking; Rtc_Clkout And Clkout32K Clocking - NXP Semiconductors MKL27Z128VFM4 Reference Manual

5.7.3 RTC clocking

The RTC module can be clocked as shown in the following figure.
The chosen clock must remain enabled if the RTC is to
continue operating in all required low-power modes.

5.7.4 RTC_CLKOUT and CLKOUT32K clocking

When the RTC is enabled and the port control module selects the RTC_CLKOUT
function, the RTC_CLKOUT signal, controlled from SIM_SOPT2[RTCCLKOUTSEL],
outputs a 1 Hz or 32 kHz output derived from RTC oscillator as shown below and can be
configured to drive to external pins via pin control configuration for the associated pin. It
is also possible to drive CLKOUT32K on the same pins as controlled by
Freescale Semiconductor, Inc.
LPO
MCGIRCLK
OSCERCLK
Bus clock
SIM_COPC[COPCLKSEL]
Figure 5-2. COP clock generation
OSC32KCLK
LPO
RTC_CLKIN
SIM_SOPT1[OSC32KSEL]
Figure 5-3. RTC clock generation
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
00
01
COP clock
10
11
NOTE
00
ERCLK32K
11
(to RTC)
10
Chapter 5 Clock Distribution
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